1. Field of the Invention
The present invention relates to a coupling, and more particularly to a coupling for supporting a front fork in the head tube of a bicycle.
2. Description of the Prior Art
A typical arrangement for fixing a handle stem is disclosed in U.S. Pat. No. 4,274,301 to Katayama, filed Jun. 30, 1978, entitled "HANDLE STEM FIXING DEVICE FOR A BICYCLE". In this fixing device, an outer thread should be formed on the upper end of the front fork such that the top ball race, the top ball head cup and the nut can be threadedly engaged on the upper end of the front fork. Before the handle stem is engaged in the front fork, the ball race and the head cup should be threaded onto the front fork such that the handle stem can be fixed in place. It is inconvenient to thread the ball race and the head cup. In addition, if the handle stem is caused to rotate relative to the front fork when, for example, the bicycle falls down to the ground, it is difficult to adjust and to correct the relative position between the handle stem and the front fork, the handle stem and the front fork should be unthreaded such that the handle stem can be adjusted and fixed in the correct position.
The present invention has arisen to mitigate and/or obviate the afore-described disadvantages of the conventional handle stem fixing devices.